Linked List

Below is an example structure that represents a linked list node:

struct Node {

    // Example data field
    int data;

    // Example of the next pointer
    Node* next;
}

2. Creating a Node of Linked List
We can create the structure variables i.e. nodes using dynamic memory allocation 
and structure pointer. Although we can also do it statically, dynamic allocation is 
preferred to make full use of the abilities of the linked list.

struct Node* node2 = (struct Node*)malloc(sizeof(struct Node));

Shortening the Node Declaration
If you feel that using the struct Node* every time makes the statement 
unnecessarily complex, you can use the typedef to define an alias for it.
typedef struct node {
   int data;
   struct node* next;
}Node;

Then we can create the Node as:
Node* node2 = (Node*) malloc(sizeof(Node));

Code:

#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
    int data;
    struct Node *next;
}Node;

int main() {

    Node *first = (Node *)malloc(sizeof(Node));
    first->data = 10;

    Node *second = (Node *)malloc(sizeof(Node));
    second->data = 20;

    Node *third = (Node *)malloc(sizeof(Node));
    third->data = 30;

    first->next = second; 
    second->next = third;
    third->next = NULL;

    printf("Linked List: ");
    
    Node* temp = first;
    while(temp) {
      printf("%d ", temp->data);
      temp = temp->next;
    }

    return 0;
}

Creation of New Node using Function
#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
    int data;
    struct Node *next;
} Node;


Node *createNode(int data) {
    Node *newNode = (Node *)malloc(sizeof(Node));
    newNode->data = data;
    newNode->next = NULL;
    
    return newNode;
}

int main() {

    Node *first = createNode(10);
    first->next = createNode(20);
    first->next->next = createNode(30);

    printf("Linked List: ");
    Node *temp = first;
    while (temp)
    {
        printf("%d ", temp->data);
        temp = temp->next;
    }

    return 0;
}


In JAVA

// Linked list implementation in Java

class LinkedList {
  // Creating a node
  Node head;

  static class Node {
    int value;
    Node next;

    Node(int d) {
      value = d;
      next = null;
    }
  }

  public static void main(String[] args) {
    LinkedList linkedList = new LinkedList();

    // Assign value values
    linkedList.head = new Node(1);
    Node second = new Node(2);
    Node third = new Node(3);

    // Connect nodess
    linkedList.head.next = second;
    second.next = third;

    // printing node-value
    while (linkedList.head != null) {
      System.out.print(linkedList.head.value + " ");
      linkedList.head = linkedList.head.next;
    }
  }
}


Insertion

#include <stdio.h>
#include <stdlib.h>

// Define the node structure
typedef struct Node {
    int data;
    struct Node* next;
} Node;


Node* createNode(int data) {
    Node* newNode = (Node*)malloc(sizeof(Node));
    if (!newNode) {
        printf("Memory error\n");
        return NULL;
    }
    newNode->data = data;
    newNode->next = NULL;
    return newNode;
}


void insertAtBeginning(Node** head, int data) {
    Node* newNode = createNode(data);
    newNode->next = *head;
    *head = newNode;
}


void insertAtEnd(Node** head, int data) {
    Node* newNode = createNode(data);
    if (*head == NULL) {
        *head = newNode;
        return;
    }
    Node* temp = *head;
    while (temp->next != NULL) {
        temp = temp->next;
    }
    temp->next = newNode;
}


void insertInMiddle(Node** head, int data, int position) {
    Node* newNode = createNode(data);
    if (position == 1) {
        newNode->next = *head;
        *head = newNode;
        return;
    }
    
    Node* temp = *head;
    for (int i = 1; i < position - 1 && temp != NULL; i++) {
        temp = temp->next;
    }

    if (temp == NULL) {
        printf("Position is out of bounds\n");
        return;
    }
    
    newNode->next = temp->next;
    temp->next = newNode;
}


void printList(Node* head) {
    Node* temp = head;
    while (temp != NULL) {
        printf("%d -> ", temp->data);
        temp = temp->next;
    }
    printf("NULL\n");
}

int main() {
    Node* head = NULL;

    insertAtEnd(&head, 10);
    insertAtEnd(&head, 20);
    insertAtEnd(&head, 30);

    printf("Initial List: ");
    printList(head);

    insertAtBeginning(&head, 5);
    printf("After inserting 5 at beginning: ");
    printList(head);

    insertInMiddle(&head, 25, 3);
    printf("After inserting 25 at position 3: ");
    printList(head);

    insertAtEnd(&head, 40);
    printf("After inserting 40 at end: ");
    printList(head);

    return 0;
}